From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: bit fields && data tearing Date: Tue, 09 Sep 2014 07:18:22 -0400 Message-ID: <540EE1FE.3090706@hurleysoftware.com> References: <20140712181328.GA8738@redhat.com> <54079B70.4050200@hurleysoftware.com> <1409785893.30640.118.camel@pasglop> <063D6719AE5E284EB5DD2968C1650D6D17487172@AcuExch.aculab.com> <1409824374.4246.62.camel@pasglop> <5408E458.3@zytor.com> <54090AF4.7060406@hurleysoftware.com> <54091B30.7080100@zytor.com> <5409D76D.2070203@hurleysoftware.com> <5409D9C0.7030403@zytor.com> <20140908185240.21f52ca0@alan.etchedpixels.co.uk> <540DEE6C.2060904@zytor.com> <20140908201722.66bc6492@alan.etchedpixels.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140908201722.66bc6492@alan.etchedpixels.co.uk> Sender: linux-alpha-owner@vger.kernel.org To: One Thousand Gnomes , "H. Peter Anvin" Cc: Benjamin Herrenschmidt , David Laight , Jakub Jelinek , "linux-arch@vger.kernel.org" , Tony Luck , "linux-ia64@vger.kernel.org" , Oleg Nesterov , "linux-kernel@vger.kernel.org" , Paul Mackerras , "Paul E. McKenney" , "linuxppc-dev@lists.ozlabs.org" , Miroslav Franc , Richard Henderson , linux-alpha@vger.kernel.org List-Id: linux-arch.vger.kernel.org On 09/08/2014 03:17 PM, One Thousand Gnomes wrote: >>> I think the whole "removing Alpha EV5" support is basically bonkers. Just >>> use set_bit in the tty layer. Alpha will continue to work as well as it >>> always has done and you won't design out support for any future processor >>> that turns out not to do byte aligned stores. >>> >>> Alan >>> >> >> Is *that* what we are talking about? I was added to this conversation >> in the middle where it had already generalized, so I had no idea. >> >> -hpa > > Yes there are some flags in the tty layer that are vulnerable to this > (although they've been vulnerable to it and missing a lock since last > century with no known ill effects). That observation cuts both ways; I'm willing to leave it vulnerable with 'no known ill effects' on the Alpha. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:37953 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751300AbaIILSa (ORCPT ); Tue, 9 Sep 2014 07:18:30 -0400 Message-ID: <540EE1FE.3090706@hurleysoftware.com> Date: Tue, 09 Sep 2014 07:18:22 -0400 From: Peter Hurley MIME-Version: 1.0 Subject: Re: bit fields && data tearing References: <20140712181328.GA8738@redhat.com> <54079B70.4050200@hurleysoftware.com> <1409785893.30640.118.camel@pasglop> <063D6719AE5E284EB5DD2968C1650D6D17487172@AcuExch.aculab.com> <1409824374.4246.62.camel@pasglop> <5408E458.3@zytor.com> <54090AF4.7060406@hurleysoftware.com> <54091B30.7080100@zytor.com> <5409D76D.2070203@hurleysoftware.com> <5409D9C0.7030403@zytor.com> <20140908185240.21f52ca0@alan.etchedpixels.co.uk> <540DEE6C.2060904@zytor.com> <20140908201722.66bc6492@alan.etchedpixels.co.uk> In-Reply-To: <20140908201722.66bc6492@alan.etchedpixels.co.uk> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: One Thousand Gnomes , "H. Peter Anvin" Cc: Benjamin Herrenschmidt , David Laight , Jakub Jelinek , "linux-arch@vger.kernel.org" , Tony Luck , "linux-ia64@vger.kernel.org" , Oleg Nesterov , "linux-kernel@vger.kernel.org" , Paul Mackerras , "Paul E. McKenney" , "linuxppc-dev@lists.ozlabs.org" , Miroslav Franc , Richard Henderson , linux-alpha@vger.kernel.org Message-ID: <20140909111822.nSdJO-mOif8I7trSpgVJwRC5TjIZD1UzDbvoPN-4JuU@z> On 09/08/2014 03:17 PM, One Thousand Gnomes wrote: >>> I think the whole "removing Alpha EV5" support is basically bonkers. Just >>> use set_bit in the tty layer. Alpha will continue to work as well as it >>> always has done and you won't design out support for any future processor >>> that turns out not to do byte aligned stores. >>> >>> Alan >>> >> >> Is *that* what we are talking about? I was added to this conversation >> in the middle where it had already generalized, so I had no idea. >> >> -hpa > > Yes there are some flags in the tty layer that are vulnerable to this > (although they've been vulnerable to it and missing a lock since last > century with no known ill effects). That observation cuts both ways; I'm willing to leave it vulnerable with 'no known ill effects' on the Alpha.